Conventional water supports for people, also known as personal flotation devices (PFDs), usually have the form of a vest or jacket worn on the upper body of the wearer. This locates the buoyancy relatively high on the torso, so that the wearer's head is above the water, which is desirable for cases where the wearer may be weak or unconscious, or where current or waves are present.
In quiet water such as in a pool or in a lake, people may sometimes want simply to lounge or float in the water, say on a hot day. Inflatable mattresses and foam mattresses and sausages have commonly served this purpose, but they do not allow for controlled and consistent immersion of the user in the water, and they lack stability and reliable support for the user.